Gates said that the report's findings indicated only a "low risk" of repeal, noting that more than two-thirds of "tens of thousands of troops and their families" who responded to a survey indicated that they do not object to gays and lesbians serving openly in uniform. But he acknowledged that about 40 percent to 60 percent of troops serving in predominantly all-male ground combat specialties -- mostly Army and Marines -- predicted a negative impact if the current ban is repealed.

"Those findings and the potential implications for America's fighting forces remain a concern to service chiefs and to me," Gates said at a Pentagon new conference, noting that this has made the service chiefs "less sanguine" about repeal in regard to the impact a repeal would have on the readiness of ground combat units.

But Gates said he was determined to "minimize any negative impact" that repealing the ban would have on troops or their units. "This can be done and should be done without risk to combat readiness," he said.

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, who joined Gates in publicly voicing support for repeal, said he endorsed the results of the working group responsible for the study, which he said was given the "tall order" of assessing the best way to implement a change in the 1993 "don't ask, don't tell" policy across all the armed services.

"And so for the first time the Chiefs and I have more than just anecdotal evidence and hearsay to inform the advice we give our civilian leaders," Mullen said in his prepared statement, adding that he and the chiefs met with Obama as recently as yesterday.

The findings add pressure on the Senate, with only three weeks left in an already overbooked lame-duck session, to pass a fiscal 2011 defense authorization bill with a repeal provision. Obama and senior administration officials have long stated their support for a legislative repeal of "don't ask, don't tell," preferring to have Congress approve language that would allow for an "orderly" implementation of a dramatic change for the military over leaving the decision to the courts.

Gates said that he did not know exactly how long it would take to implement the change in policy, and stressed that Congress should end the ban this year to prevent the courts from abruptly making changes. He said he preferred to take a "careful and considered approach" that he said Congress and the pending legislation would allow him.

"The key to success as with most things military is training, education-- and above all strong and principled leadership-- throughout the chain of command," he said.

The version of the fiscal 2011 defense authorization bill approved by the Senate Armed Services Committee contains language that would repeal the 1993 ban after the Pentagon certifies that doing so will not affect unit cohesion, troop morale, or combat readiness. The House has already passed its version of the defense bill, with an amendment added during floor debate identical to the Senate Armed Services Committee's repeal language.

Release of the Pentagon's report today may have minor impact on Senate Democrats' effort to pass the defense authorization bill. Senate Armed Services Committee Chairman Carl Levin, D-Mich., said the challenge remains winning floor time and the votes of Sen. Susan Collins, R-Maine, and one or two more Senate Republicans to line up 60 votes. Collins is a "good indicator of whether or not the floor process" satisfies Republicans, Levin said today.

Levin said Collins and other Republicans want enough floor time to ensure an open amendment process, which may be difficult to guarantee with the tight schedule. Last year, defense authorization required more than a week of floor time, and spending too much time on the latest authorization bill would crowd out work on other priority issues such as the fate of the expiring Bush-era tax cuts.

After Levin's committee holds hearings on the Pentagon's report Thursday and Friday, Democratic aides said voting on the authorization bill could start next week. Timing will be determined by Senate Majority Leader Harry Reid, D-Nev., Levin said. Aides said a motion queuing up action on the bill may be among several procedural moves Reid makes late this afternoon.

In what Gates called the "most thorough and objective reviews ever" on military personnel issues, the Pentagon working group spoke with many gays and lesbians serving in the armed forces. Troops and some 40,000-45,000 spouses, as well as proponents and opponents of the repeal were also consulted, Gates said.

"However low the overall risk of repeal may be with respect to readiness, cohesion and retention, it is not without its challenges," Mullen said. "We can best address those challenges by having it within our power and our prerogative to manage the implementation process ourselves."

Existing personnel and housing policies should be adapted to accommodate gays and lesbians, said Gates, who emphasized that this did not pose "insurmountable" challenges.

To assess the impact of repealing the ban, the Pentagon report included survey results to questions about personal lifestyle issues that could be affected by allowing homosexuals to serve openly.

About half the service members surveyed reported that they already have been assigned to "open-bay showers" that are shared by soldiers they believe to be homosexual. Of those, 73 percent said they would either take no action, talk to the person, or avoid taking showers at the same time if the ban on openly gay troops is lifted. Only 14.5 percent said they would speak with a leader about options for showering.

Only about 18 percent of the service members said they would "probably move off base" if they lived in military base housing and a gay or lesbian soldier and partner also lived there.

Survey participants also were asked if they would stop attending military social functions if a gay or lesbian service member attended with a partner. Forty-seven percent of service members who attend events with family members said they would continue to do so, with about 33 percent saying they would likely stop attending. About 6 percent said they would attend alone.